Axial thermal dispersion and particle to fluid transfer in packed-fluidized beds

Abstract In a packed-fluidized bed small particles are fluidized in the interstices of large particles. The dynamic responses of three packed-fluidized beds have been analysed within the large particle Reynolds number range from 50 to 300; both pulse response and experimental frequency response were recorded. A theory previously given has been used to analyse the experimental responses in terms of the coefficient of thermal dispersion, particle to fluid heat transfer coefficient and intraparticle thermal conductivity; the parameters have been found from the experimental responses by nonlinear regression. The principal reason for the good thermal properties of the bed appears to be due to a large increase in thermal dispersion within the bed because of the fluidised particles. Intraparticle thermal conductivities found from the responses agreed with probable true values, and particle to fluid heat transfer coefficients were similar to those found for fixed and fluidized beds.